Redefinition of the Dinoflagellate Genus Alexandrium Based on Centrodinium: Reinstatement of Gessnerium and Protogonyaulax, and Episemicolon gen. nov. (Gonyaulacales, Dinophyceae)Read the full article
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The Effect of Extraction Conditions on Chemical and Thermal Characteristics of Kappa-Carrageenan Extracted from Hypnea bryoides
Hypnea bryoides collected from the Arabian Sea on the southern coast of Oman was investigated for κ-carrageenan optimal extraction conditions. The effects of different conditions of alkali treatment (4, 6, and 8% w/v NaOH), temperatures (70, 75, and 80°C), and time (2, 2.75, 3.5 hours) on carrageenan yield and chemical and thermal properties were evaluated. Yield was significantly affected by alkaline concentration and temperature, with highest value of 26.74 ± 5.01%. Molecular weights of the extracted carrageenan were significantly reduced by increased temperatures and ranged from 5.95 ± 0.49 × 105 Da to 13.90 ± 0.14 × 105. FTIR showed that samples under all extraction conditions were similar and confirmed the presence of κ-carrageenan with no traces of μ-precursor. Sulfate content was also significantly reduced by alkaline concentration (from 4% to 6%) and ranged from 7.62 ± 5.52% to 17.02 ± 0.14. Thermal properties showed more sensitivity towards temperature and alkaline strength parameter than time. In addition, melting and gelling temperatures were significantly correlated with the molecular weight, but not sulfate content. In conclusion, mild extraction conditions were found to be more efficient in introducing the intended structural modification while getting the highest yield and quality.
Photosynthetic Pigments Contained in Surface Sediments from the Hydrothermal System of Guaymas Basin, Gulf of California
In the exploration of the hydrothermal system of the Guaymas Basin (GB) between 27° 00′ 35′′ and 27° 00′ 50′′ N and 111° 24′ 15′′ and 111° 24′ 40′′ W in the Gulf of California, carried out on the R/V Atlantis and of the DSRV/Alvin in October 2008, four cores of surface sediments were obtained to analyse photosynthetic pigments at two locations with contrasting extreme conditions: Oil Town and Great Pagoda. We identified nine pigments: Chlorophyll-a, Phaeophytin-a, Phaeophorbide-a, Pyropheophytin-a (degradation Chlorophyll-a products), β-Carotene, Alloxanthin, Zeaxanthin, Diadinoxanthin, and Prasinoxanthin (carotenoids). The maximum pigment concentration was registered in the Great Pagoda (10,309 ng/g) and the minimum in Oil Town (918 ng/g). It is demonstrated that photosynthetic pigment profiles in surface sediments depend on the heterogeneity of the extreme conditions of each site caused mainly by temperature and bacterial substrates. Therefore, there were significant differences (p <0.05) in the pigmentary profile of the four sedimentary cores analyzed. However, no statistical differences (p > 0.05) in the concentration of pigments have been detected. We conclude that the photosynthetic pigments contained in the surface sediments of the hydrothermal vents in the Guaymas Basin are primarily of chemoautotrophic bacterial origin.
Against Common Assumptions, the World’s Shark Bite Rates Are Decreasing
The trends of the world’s top ten countries relating to shark bite rates, defined as the ratio of the annual number of shark bites of a country and its resident human population, were analyzed for the period 2000-2016. A nonparametric permutation-based methodology was used to determine whether the slope of the regression line of a country remained constant over time or whether so-called joinpoints, a core feature of the statistical software Joinpoint, occurred, at which the slope changes and a better fit could be obtained by applying a straight-line model. More than 90% of all shark bite incidents occurred along the US, Australia, South Africa, and New Zealand coasts. Since three of these coasts showed a negative trend when transformed into bite rates, the overall global trend is decreasing. Potential reasons for this decrease in shark bite rates—besides an increase in the world’s human population, resulting in more beach going people, and a decrease of sharks due to overfishing—are discussed.
Socioeconomic Determinants of Mangrove Exploitation and Seagrass Degradation in Zanzibar: Implications for Sustainable Development
The concept of “sustainability” has become the current answer to absolving the world of its environmental and economic crises in the 21st century. This paper analyses seven socioeconomic factors (age of household head, household average annual income, marital status of household head, gender of household head, household size, education level of household head, and period of residence of household head) influencing extreme degradation of seagrass and exploitation of mangrove resources in Zanzibar, Tanzania. To accomplish this, Participatory Rural Appraisal approaches and household questionnaire survey were used to obtain information on primary data. Multiple regression analysis and descriptive statistics were used to analyze quantitative data while content analysis was used to analyse qualitative data. The findings revealed that all the socioeconomic variables tested were statistically significant (P<0.05) and had an influence on the exploitation of mangrove and degradation of seagrass except gender of the household (P=0.88) and household annual average income (P=0.655), respectively. In addition, statistical analysis revealed that there was significant difference in the mangrove status between the sites (p= 0.0001, χ2 =27.27) with more exploitation at Charawe compared to Kibele village, whereas no significant differences were revealed in the status of seagrass between the two sites (p= 0.2693, χ2 =1.2202). On one hand, the findings revealed that at Kibele and Charawe 60% and 50% practice gleaning, 40% and 55% are engaged in seaweed farming, and 60% and 70% collect bait from seagrass meadows, respectively. All these activities had direct influence on seagrass status. On the other hand, the finding revealed that livelihood needs, population growth, level of education, and lack of alternative source of income are the key drivers to exploitation of coastal natural resources especially mangrove and seagrasses. To ensure sustainable exploitation of coastal resources alternative livelihood activities such as farmed fish, small/petty business, and agriculture activities that are profitable and easy to manage should be introduced to the local coastal community to enhance active participation in conserving resources and improving their livelihood.
Variation in Righting Times of Holothuria atra, Stichopus chloronotus, and Holothuria edulis in Response to Increased Seawater Temperatures on Heron Reef in the Southern GBR
Sea cucumbers can mitigate some impacts of climate change through digestion of benthic sands and production of calcium carbonate. The projected ecological benefits of sea cucumbers in warmer, more acidic oceans are contingent on the capacities of individuals to acclimate and populations to adapt to climatic changes. The goal of this experiment was to evaluate the degree to which warming waters would impact three abundant species of sea cucumbers on the Heron Reef in Queensland, Australia. We conducted a behavioral assay using three species of sea cucumbers, Holothuria atra, Stichopus chloronotus, and Holothuria edulis. Individuals from each species were subjected to three conditions mimicking current summer temperatures, current winter temperatures, and an elevated temperature consistent with future ocean warming by the year 2100. Sea cucumber reactions were evaluated using righting time as a proxy for their stress levels and overall tolerance of warming events. The three sea cucumber species reacted differently to water temperature changes: H. atra’s righting times declined with temperature, S. chloronotus had greater righting times at high and low temperature extremes, and H. edulis’s righting times remained relatively constant throughout. Our results suggest that each of these species might respond differently to ocean warming and while some may be able to continue to combat climate change in benthic communities, others may decline in ecological function.
The Ulva spp. Conundrum: What Does the Ecophysiology of Southern Atlantic Specimens Tell Us?
Species of the genus Ulva are common in anthropogenically disturbed areas and have been reported as the cause of green tides in many areas of the world. In addition, they rank among the main marine groups used in a wide range of commercial applications. By displaying few distinctive morphological characters, some taxonomical identifications are difficult and the genus is under a conundrum. Our aims were to provide ecophysiological information about three Ulva species in response to abiotic factors and to evaluate the proposal of ecophysiological information and the chlorophyll-a fluorescence technique as auxiliary tool to resolve the long-standing taxonomic confusion. We hypothesize that three cooccurring specimens (U. fasciata Delile, U. lactuca Linnaeus, and U. rigida C. Agardh) have different ecophysiological responses (as measured by the effective quantum yield of photosystem II by pulse amplitude modulated fluorometers) under manipulated conditions of temperature and nutrient concentration. Ulva lactuca and U. rigida showed different photosynthetic efficiencies related to temperature, whereas no difference was recorded for U. fasciata individuals. These results provide a reasonable explanation for the variability in spatial and temporal abundance of these species of Ulva on rocky shores. We proposed the use of ecophysiological information by chlorophyll-a fluorescence as an auxiliary tool to corroborate the taxonomic distinction of Ulva species. We reinforce the statement of U. fasciata and U. lactuca as distinct valid species.